Stamp



FIG. 1 is a perspective view of a design for a stamp showing my new design;

FIG. 2 is a front elevation thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a side elevation thereof, the side opposite being a mirror image.

The broken lines are provided for illustrative purposes only, and form no part of the claimed design. 

The ornamental design for a stamp, as shown and described. 